Typical boiler tube arrays of the type used to transfer heat from a combustion chamber to a fluid driving a power-generating device in an industrial power plant may include as many as a hundred boiler tubes in a single, ideally parallel array. Because the long, relatively thin-walled tubes are subjected to significant heat stress, they tend to warp and shift out of parallel alignment, reducing the uniformity and efficiency of heat transfer to the fluid in the tubes.
The industry standard for keeping the tubes in proper alignment is a boiler tube cuff, comprising an elongated set of mating handcuff-like castings with semi-circular cuff portions designed to be radially mated over a set of boiler tubes. After being placed over a set of tubes in the array, the mating halves of a cuff set are secured to one another with known structure such as weldable posts or threaded bolts. The warping and misalignment of the tubes typically requires the tubes to be pre-clamped in parallel before the cuffs can be mated over them.
Most boiler tube cuffs come in lengths capable of holding five or six tubes at a time. However, each set of five or so cuffed tubes is prone to distortion and misalignment relative to adjacent sets of cuffed tubes, partially defeating the alignment purpose of the cuffs. Occasionally, a cuff set will be produced with as many as twelve or fifteen "holes", but this is considered an extreme length in the industry, and is impractical for most applications because it is too costly to make a longer mold.